D047 Assessment of Mechanical Wellbore Stability by Numerical Analysis of Fracture Growth I. Moeck (GFZ - GeoForschungsZentrum Potsdam) T. Backers* (GeoFrames GmbH) & H. Schandelmeier (Technical University Berlin) SUMMARY One of the most crucial aspects of drilling operation is wellbore stability. Especially in geothermal energy projects it can jeopardy the drilling process and financial plans. The mechanical instability phenomena at the borehole wall are borehole breakouts representing fracture networks. Therefore the understanding of initiation and growth of breakouts plays an important role in wellbore stability assessment. This paper presents a new method to calculate breakout growth by fracture mechanics based